On 28/12/20 10:42 pm, Andy Shevchenko wrote:
On Mon, Dec 28, 2020 at 07:19:49PM +0800, Brad Campbell wrote:
G'day Andy,
Commit 306c54d0edb6ba94d39877524dddebaad7770cf2 in kernel 5.9 breaks
usb-audio on my machine.
I have a 2011 iMac with a pair of Apple Thunderbolt displays. Both Thunderbolt
displays have internal usb-audio devices. This patch causes the audio to stutter
terribly. Reverting it resolves the issue on any kernel up to and
including 5.10.3.
Booting with pci=nomsi fixes the audio issues, but causes all sorts of
other problems (like broken Thunderbolt display routing), so that's a non-starter.
The usb audio devices would appear to be on the Pericom USB controllers in the displays.
It wouldn't be the first peculiarity I've had on this machine due to the early Thunderbolt
implementation.
The issue is pretty much identical with the sound card on both monitors.
Thanks for the report!
Funny that previous mail in my mailbox is exactly about this issue for
PI7C9X440SL, i.e. fix [1] I made for v5.11 and Sasha ported to v5.10
(mentioned previous mail). Can you try to apply [1] and confirm issue gone?
G'day Andy,
Can't ask for better than that. Yes, that patch on 5.10.3 solves the problem nicely.
Now I know what to look for, it's in 5.10.4.
Regards,
Brad
--
An expert is a person who has found out by his own painful
experience all the mistakes that one can make in a very
narrow field. - Niels Bohr
